A COMPUTATIONAL SCHEME FOR MODELING THE PROCESS OF MULTICOMPONENT MIXTURE FRACTIONATION

From the equations of the component-by-component material balance of the contact stage and the phase equilibrium of the components, a system of linear equations with respect to the concentrations of the components is obtained. The matrix of the system is ribbon, tridiagonal without a pronounced diagonal predominance of elements. The value of the determinant of the matrix of the system is close to zero, we have a weakly conditioned system. The conditionality of the system can be improved somewhat by introducing a fictitious stage for the feed stream, eliminating the mass-heat exchange contact of liquid flows and a pair of adjacent stages. In this case, a strict diagonal predominance of the element is ensured on the step. For a complex distillation column with a side stripping section, the number of rows and columns of the matrix is increased by the number of contact steps of the stripping section. There are also no supra- and sub-diagonal elements in the cube zone of the column - the top of the stripping section. The next feature is the presence of non-zero elements outside the diagonals corresponding to the input of the liquid flow from the column into the stripping section and the output of the steam flow from the stripping section into the column. The quasi-precision of the matrix makes it possible to form a calculation scheme in the form of a single multithreaded column with corresponding connections between the steps. In a multithreaded column, the number of calculated steps is greater than the number of actual contact steps by the amount of the number of fictitious steps. The representation of the column complex in the form of a single multithreaded column contributes to the successful execution of calculations using a sequential iterative point-by-point method.